Compared with a liquid crystal display (LCD), an organic light-emitting diode (OLED) display apparatus has the advantages of rapid response speed, light weight, flexibility, wide viewing angle, etc. Active-matrix OLEDs (AMOLEDs) further have the advantages of small drive current and low power consumption and are applicable for high-resolution display.
Thin-film transistors (TFTs) taken as control switches are arranged in both the LCD and the OLED display apparatus. The TFT includes amorphous silicon (a-Si) type, polycrystalline silicon (poly-Si) type, oxide semiconductor type, organic TFT type or the like. The a-Si type or the organic TFT type has small carrier mobility and a small drive current, driving a high-brightness OLED requires a high voltage, and the device also occupies a large space. A low-temperature polysilicon (LTPS) TFT has a mobility as high as 100 cm2/V·s; the high-current characteristic of the LTPS TFT satisfy the exact demands of an OLED well; and the service life of the OLED is prolonged due to a low operating voltage and a high-density driver architecture. Meanwhile, in order to overcome the compensating circuit relevant to gray scale and panel uniformity, a single pixel of the display apparatus tends to be provided with a plurality of TFTs. Moreover, due to the high-density local feature of LTPS, an OLED panel with high brightness and high image quality can be obtained more easily. Currently, most of the successfully commercially produced AMOLEDs adopt LTPS TFT array substrates.